The more dramatic effect was on a particular set of endpoints that have a relative high traffic (it peaks at 1000 req/s) that was killing the app, making upset our relational database (with frequent deadlocks) and driving our Elasticsearch cluster crazy.

We did more than just split the endpoints into microservices. We also designed the new system to be more resilient. We changed our persistence strategy to make it more sensible to our traffic using a distributed key-value database and designed documents accordingly.

The result was very dramatic, like entering into a loud club and suddenly everything goes silent. No more outages, very consistent response times, the instances scaled with traffic increase very smoothly and in overall a more robust system.

The moral of this experience (at least for me) is that breaking a monolith app into pieces has to have a purpose and implies more than just move the code to several services keeping the same strategy (that's actually slower, time consuming and harder to monitor)